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It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

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Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#91

Post by dgently7 »

overvale wrote: post #12
somat wrote: post #10

Earlier quoted context omitted.

With regards to the sodium vapor process, an idea has been percolating in the back of my head ever since I saw that video. But I don't really have the budget to try it out. theory: make the mask out of non-visable light illuminate the backing screen in near Infra-Red light. (after a bit of thought I chose near-IR as opposed to near-UV for hopefully obvious reasons) point two cameras at a splitting prism with a near I…

Debevec tried a version of this: https://arxiv.org/abs/2306.13702

im familiar with this work and specifically they tried replicating the sodium vapor style approach but what worked for poppins level isnt actually good enough for today. Specifically you still end up with light spill that contaminates the foreground, especially for things like the fresnel reflections on the side of a face. the magenta idea was to still do what is basically a color difference key, but increase the color separation between fg and bg by lighting the two with different opposite colored lights. then using a ml model to recover the original fg color.

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#92

Post by dgently7 »

actionfromafar wrote: post #16
somat wrote: post #10

Earlier quoted context omitted.

With regards to the sodium vapor process, an idea has been percolating in the back of my head ever since I saw that video. But I don't really have the budget to try it out. theory: make the mask out of non-visable light illuminate the backing screen in near Infra-Red light. (after a bit of thought I chose near-IR as opposed to near-UV for hopefully obvious reasons) point two cameras at a splitting prism with a near I…

I'll do you one better, which requires no special cameras (most have IR filters) nor double cameras or prisms. Shoot the scene in 48 or 96 fps. Sync the set lighting to odd frames. Every odd frame, the set lights are on. Every even frame, set lights are off. For the backing screen, do the reverse. Even frames, the backing screen is on. Odd frames, backing screen is off. There you go. Mask / normal shot / Mask normal…

this is the approach that stop motion uses, except they get to keep the camera in the same place. its still not perfect because of spill from the background onto the foreground and requires additional masking and cleanup.

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#93

Post by dgently7 »

dylan604 wrote: post #33

The sad thing about this is the problems encountered during post from the production team saying "fix it post" during the shoot. I've been on set for green screen shoots where the lighting was not done properly. I watched the gaffer walk across the set taking readings from his meter before saying the lighting was good. I flip on the waveform and told him it was not even (which never goes down well when camera dept te…

didnt dune win a vfx oscar and their screens werent even green at all? they were tan like sand.

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#94

Post by Sniffnoy »

comex wrote: post #8

See also this video comparing Corridor Key to traditional keyers: https://www.youtube.com/watch?v=abNygtFqYR8

Summary: He created 4 hard-to-key shots, and on each of them tried KeyLight, IBK, and Corridor Key. Overall on 3 of them he judged that Corridor Key had done the best job, on one of them he judged that IBK had done the best job. I think on all of them he judged that more work was still necessary, none of them was fully usable as-is.

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#95

Post by lynnharry »

It’s fascinating to see the bridge between academic research and industry application here. While Image Matting is a massive research area in Computer Vision, academia often focuses on solving perfect 'benchmarks.' Corridor Crew effectively took that foundational research, like neural unmixing and synthetic training, and adapted it to solve the 'messy' reality of production, like tracking markers and motion blur. It’s a great example of using open-source deep learning resources to build a tool that prioritized workflow over just a high accuracy score.

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#96

Post by krackers »

ralusek wrote: post #9

I'm a software engineer that, like the vast majority of you, uses AI/agents in my workflow every day. That being said, I have to admit that it feels a little weird to hear someone who does not write code say that they built something, without even mentioning that they had an agent build it (unless I missed that).

It's actually a bit refreshing that they didn't brand this with the usual "LLM hype". And it's actually a good example of someone using LLMs to solve a problem by bringing in their domain knowledge. (The solution is surprisingly simple though, I wonder if other people have done this before but kept it proprietary/in-house).

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#97

Post by plastic3169 »

dgently7 wrote: post #93
dylan604 wrote: post #33

The sad thing about this is the problems encountered during post from the production team saying "fix it post" during the shoot. I've been on set for green screen shoots where the lighting was not done properly. I watched the gaffer walk across the set taking readings from his meter before saying the lighting was good. I flip on the waveform and told him it was not even (which never goes down well when camera dept te…

didnt dune win a vfx oscar and their screens werent even green at all? they were tan like sand.

Yes and it was a massive manual effort. In a way they acknowledged that keying does not really work all the way and having that unnatural color everywhere in the set is not worth it. It’s a massive production with heavy VFX work so not something you can apply to your own production. Sand screen and roto sections of this discussion are interesting.

https://youtu.be/UARrOsNPviA

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#98

Post by actionfromafar »

wlesieutre wrote: post #79
actionfromafar wrote: post #70

Earlier quoted context omitted.

So, shoot at 240 fps and strobe set lights for 1/240s and backdrop for 1/240s.

And if you want a slower than 1/240th second shutter speed, no you don't

Or... you frame blend in Fusion or go full hog in Nuke.

( https://www.nukepedia.com/tools/gizmos/time/vectorframeblend... )

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#99

Post by regularfry »

wiml wrote: post #21
somat wrote: post #10

Earlier quoted context omitted.

With regards to the sodium vapor process, an idea has been percolating in the back of my head ever since I saw that video. But I don't really have the budget to try it out. theory: make the mask out of non-visable light illuminate the backing screen in near Infra-Red light. (after a bit of thought I chose near-IR as opposed to near-UV for hopefully obvious reasons) point two cameras at a splitting prism with a near I…

This approach was used in the 1950s/60s with ultraviolet light (rather than IR) to create a traveling matte. I'm not sure why visible-light techniques won out. Easier to make sure that the illumination is set up correctly, maybe?

Or maybe they didn't want to blind the talent. UV isn't something you want to bathe your retinas in.

Re: It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

#100

Post by steve_adams_86 »

tekacs wrote: post #29
ralusek wrote: post #9

I'm a software engineer that, like the vast majority of you, uses AI/agents in my workflow every day. That being said, I have to admit that it feels a little weird to hear someone who does not write code say that they built something, without even mentioning that they had an agent build it (unless I missed that).

Worth bearing in mind that people in VFX are often relatively technical. From their own 'LLM handover' doc: https://github.com/nikopueringer/CorridorKey/blob/main/docs/... > Be Proactive: The user is highly technical (a VFX professional/coder). Skip basic tutorials and dive straight into advanced implementation, but be sure to document math thoroughly.

Back when I played with animation and post pipelines, I was writing a decent amount of python. It's part of how I got into programming. At the time I would have said I can't program, and I suspect this guy is similar.
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